Barrier membranes including a barrier layer employing aliphatic thermoplastic urethanes

ABSTRACT

The present invention relates to membranes including a barrier layer which includes a blend of one or more aliphatic thermoplastic urethanes and one or more polar and partially crystalline materials. Under multi-layered embodiments, the barrier layer is laminated to at least one other layer formed from thermoplastic urethane, wherein the membranes are characterized in that hydrogen bonds are formed between the first layer of thermoplastic urethane and the second layer from the blend of aliphatic thermoplastic urethane and a copolymer of ethylene and vinyl alcohol.

FIELD OF THE INVENTION

[0001] The present invention relates to barrier membranes and, moreparticularly, to barrier membranes which, under certain embodiments,serve to selectively control the diffusion of gases through themembrane. Additionally, under certain embodiments, the membrane not onlyselectively controls the diffusion of gases through the membrane, butalso allows for the controlled diffusion of gases normally contained inthe atmosphere.

[0002] For a further understanding of the scope of the presentinvention, reference can be made to U.S. patent application Ser. No.08/299,287, entitled “Cushioning Device With Improved Flexible BarrierMembrane” which was filed on Aug. 31, 1994; U.S. patent application Ser.No. 08/299,286 entitled “Laminated Resilient Flexible Barrier Membranes”which was filed on Aug. 31, 1994; and U.S. patent application Ser. No.______, entitled “Barrier Membranes Including A Barrier Layer EmployingPolyester Polyols” which is commonly owned and has been filedconcurrently herewith; each of the aforementioned patent applicationsbeing expressly incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0003] Barrier membranes useful for containing fluids, including liquidsand/or gases, in a controlled manner have been employed for years in awide variety of products ranging from bladders useful in inflatableobjects, such as vehicle tires and sporting goods for example; toaccumulators used on heavy machinery; to cushioning devices useful infootwear. Regardless of the intended use, barrier membranes mustgenerally be flexible, resistant to environmental degradation andexhibit excellent gas transmission controls. Often, however, materialswhich exhibit acceptable flexibility characteristics tend to have anunacceptably low level of resistance to gas permeation. In contrast,materials which exhibit an acceptable level of resistance to gaspermeation tend to have an unacceptably low level of flexibility.

[0004] In an attempt to address the concerns of both flexibility andimperviousness to gases, U.S. Pat. No. 5,036,110 which issued Jun. 30,1991, to Moreaux describes resilient membranes for fittinghydropneumatic accumulators. According to Moreaux '110, the membranedisclosed consists of a film formed from a graft polymer which is thereaction product of an aromatic thermoplastic polyurethane with acopolymer of ethylene and vinyl alcohol (EVOH), with this film beingsandwiched between layers of thermoplastic polyurethane to form alaminate. While Moreaux '110 attempts to address the concerns in the artrelating to flexibility and imperviousness to gases, a perceiveddrawback of Moreaux is that the film described is not processableutilizing conventional sheet extrusion techniques. Thus, the presentinvention is directed to barrier membranes which are flexible, have goodresistance to gas transmission, and under certain embodiments areprocessable into laminates utilizing conventional sheet extrusiontechniques which are highly resistant to delamination.

[0005] While it should be understood by those skilled in the art uponreview of the following specification and claims that the barriermembranes of the present invention have a broad range of applications,including but not limited to bladders for inflatable objects such asfootballs, basketballs, soccer balls and inner tubes; films for foodpackaging; as well as the production of fuel lines and fuel storagetanks to name a few, still other highly desirable applications includetheir use in forming accumulators which are operable under high pressureenvironments.

[0006] For convenience, but without limitation, the barrier membranes ofthe present invention will hereinafter generally be described in termsof either accumulators or in terms of still another highly desirableapplication, namely for cushioning devices used in footwear. In order tofully discuss the applicability of the barrier membranes in terms ofcushioning devices for footwear, a description of footwear in general isbelieved to be necessary.

[0007] Footwear, or more precisely, shoes generally include two majorcategories of components namely, a shoe upper and the sole. The generalpurpose of the shoe upper is to snugly and comfortably enclose the foot.Ideally, the shoe upper should be made from an attractive, highlydurable, yet comfortable material or combination of materials. The sole,which also can be made from one or more durable materials, isparticularly designed to provide traction, protect the wearer's feet andbody during use which is consistent with the design of the shoe. Theconsiderable forces generated during athletic activities require thatthe sole of an athletic shoe provide enhanced protection and shockabsorption for the feet, ankles and legs of the wearer. For example,impacts which occur during running activities can generate forces of upto 2-3 times the body weight of an individual while certain otheractivities such as, for example, playing basketball have been known togenerate forces of up to approximately 6-10 times an individual's bodyweight. Accordingly, many shoes and, more particularly, many athleticshoes are now provided with some type of resilient, shock-absorbentmaterial or shock-absorbent components to cushion the user duringstrenuous athletic activity. Such resilient, shock-absorbent materialsor components have now commonly come to be referred to in the shoemanufacturing industry as the midsole.

[0008] It has therefore been a focus of the industry to seek midsoledesigns which achieve an effective impact response in which bothadequate shock absorption and resiliency are appropriately taken intoaccount. Such resilient, shock-absorbent materials or components couldalso be applied to the insole portion of the shoe, which is generallydefined as the portion of the shoe upper directly underlining theplantar surface of the foot.

[0009] A particular focus in the shoe manufacturing industry has been toseek midsole or insert structure designs which are adapted to containfluids, in either the liquid or gaseous state, or both. Examples ofgas-filled structures which are utilized within the soles of shoes areshown in U.S. Pat. No. 900,867 entitled “Cushion for Footwear” whichissued Oct. 13, 1908, to Miller; U.S. Pat. No. 1,069,001 entitled“Cushioned Sole and Heel for Shoes” which issued Jul. 29, 1913, to Guy;U.S. Pat. No. 1,304,915 entitled “Pneumatic Insole” which issued May 27,1919, to Spinney; U.S. Pat. No. 1,514,468 entitled “Arch Cushion” whichissued Nov. 4, 1924, to Schopf; U.S. Pat. No. 2,080,469 entitled“Pneumatic Foot Support” which issued May 18, 1937, to Gilbert; U.S.Pat. No. 2,645,865 entitled “Cushioning Insole for Shoes” which issuedJul. 21, 1953, to Towne; U.S. Pat. No. 2,677,906 entitled “CushionedInner Sole for Shoes and Method of Making the Same” which issued May 11,1954, to Reed; U.S. Pat. No. 4,183,156 entitled “Insole Construction forArticles of Footwear” which issued Jan. 15, 1980, to Rudy; U.S. Pat. No.4,219,945 entitled “Footwear” which issued Sep. 2, 1980, also to Rudy;U.S. Pat. No. 4,722,131 entitled “Air Cushion Shoe Sole” which issuedFeb. 2, 1988, to Huang; and U.S. Pat. No. 4,864,738 entitled “SoleConstruction for Footwear” which issued Sep. 12, 1989, to Horovitz. Aswill be recognized by those skilled in the art, such gas filledstructures often referred to in the shoe manufacturing industry as“bladders” typically fall into two broad categories, namely (1)“permanently” inflated systems such as those disclosed in U.S. Pat. Nos.4,183,156 and 4,219,945 and (2) pump and valve adjustable systems asexemplified by U.S. Pat. No. 4,722,131. By way of further example,athletic shoes of the type disclosed in U.S. Pat. No. 4,182,156 whichinclude “permanently” inflated bladders have been successfully soldunder the trade mark “Air Sole” and other trademarks by Nike, Inc. ofBeaverton, Oreg. To date, millions of pairs of athletic shoes of thistype have been sold in the United States and throughout the world.

[0010] The permanently inflated bladders are typically constructed undermethods using a flexible thermoplastic material which is inflated with alarge molecule, low solubility coefficient gas otherwise referred to inthe industry as a “super gas,” such as SF₆. By way of example, U.S. Pat.No. 4,340,626 entitled “Diffusion Pumping Apparatus Self-InflatingDevice” which issued Jul. 20, 1982, to Rudy, which is expresslyincorporated herein by reference, discloses a pair of elastomeric,selectively permeable sheets of film which are formed into a bladder andthereafter inflated with a gas or mixture of gases to a prescribedpressure which preferably is above atmospheric pressure. The gas orgases utilized ideally have a relatively low diffusion rate through theselectively permeable bladder to the exterior environment while gasessuch as nitrogen, oxygen and argon which are contained in the atmosphereand have a relatively high diffusion rate are able to penetrate thebladder. This produces an increase in the total pressure within thebladder, by the addition of the partial pressures of the nitrogen,oxygen and argon from the atmosphere to the partial pressures of the gasor gases contained initially injected into the bladder upon inflation.This concept of a relative one-way addition of gases to enhance thetotal pressure of the bladder is now known as “diffusion pumping.”

[0011] Under the diffusion pumping system and depending upon the bladdermaterial used and the choice of gas or gases contained therein, there isa period of time involved before a steady state of internal pressure isachieved. For example, oxygen tends to diffuse into the bladder ratherquickly with the effect being an increase in the internal pressure ofapproximately 2.5 psi. In contrast, over the course of a number of weeksnitrogen gas will gradually diffuse into the bladder resulting in anincrease of pressure to approximately 12.0 psi. The gradual increase inbladder pressure typically causes an increase in tension in the bladderskin, resulting in a volume increase due to stretching. This effect iscommonly referred to in the industry as “tensile relaxation” or “creep.”Thus, it is of significant importance which materials are chosen for thebladder and the choice of the captive gas mixture utilized to initiallyinflate the bladder to achieve a bladder which is essentiallypermanently inflated at a desired internal pressure and which maintainsa desired internal pressure over an extended period of time.

[0012] With regard to the systems utilized within the shoe manufacturingindustry prior to and shortly after the introduction of the Air Sole™athletic shoes, many of the midsole bladders consisted of a single layergas barrier type films made from polyvinylidene chloride based materialssuch as Saran® (which is a registered trademark of the Dow Chemical Co.)and which by their nature are rigid plastics, having relatively poorflex fatigue, heat sealability and elasticity. Still further, bladderfilms made under techniques such as laminations and coatings whichinvolve one or more barrier materials in combination with a flexiblebladder material (such as various thermoplastics) can potentiallypresent a wide variety of problems to solve. Such difficulties withcomposite constructions include layer separation, peeling, gas diffusionor capillary action at weld interfaces, low elongation which leads towrinkling of the inflated product, cloudy appearing finished bladders,reduced puncture resistance and tear strength, resistance to formationvia blow-molding and/or heat-sealing and R-F welding, high costprocessing, and difficulty with foam encapsulation and adhesive bonding,among others.

[0013] Yet another issue with previously known bladders is the use oftie-layers or adhesives in preparing laminates. The use of such tielayers or adhesives generally prevent regrinding and recycling of anywaste materials created during product formation back into an usableproduct, and thus, also contribute to high cost of manufacturing andrelative waste. These and other short comings of the prior art aredescribed in more extensive detail in U.S. Pat. Nos. 4,340,626;4,936,029 and 5,042,176, all of which are hereby expressly incorporatedby reference.

[0014] With the extensive commercial success of the products such as theAir Sole™ shoes, consumers have been able to enjoy a product with a longservice life, superior shock absorbency and resiliency, reasonable cost,and inflation stability, without having to resort to pumps and valves.Thus, in light of the significant commercial acceptance and success thathas been achieved through the use of long life inflated gas filledbladders, it is highly desirable to develop advancements relating tosuch products. The goal then is to provide flexible, “permanently”inflated, gas-filled shoe cushioning components which meet, andhopefully exceed, performance achieved by such products as the Air Sole™athletic shoes offered by Nike, Inc.

[0015] One key area of potential advancement stems from a recognitionthat captive gases other than the large molecule, low solubilitycoefficient “super gases” as described in the '156, '945 and '738patents utilized can be replaced with less costly and possibly moreenvironmentally friendly gases. For example, U.S. Pat. Nos. 4,936,029and 5,042,176 specifically discuss the methods of producing a flexiblebladder film that essentially maintains permanent inflation through theuse of nitrogen as the captive gas. As further described in U.S. Pat.No. 4,906,502, also specifically incorporated herein by reference, manyof the perceived problems discussed in the '029 and '176 patents aresolved by the incorporation of mechanical barriers of crystallinematerial into the flexible film such as fabrics, filaments, scrims andmeshes. Again, significant commercial success for footwear productsusing the technology described in '502 patent under the trademarkTensile Air™ sold by Nike, Inc. has been achieved. The bladders utilizedtherein are typically comprised of a thermoplastic urethane laminated toa core fabric three-dimensional, double bar Raschel knit nylon fabric,having SF₆ as the captive gas contained therein.

[0016] By way of example, an accepted method of measuring the relativepermeance, permeability and diffusion of different film materials is setforth in the procedure designated as ASTM D-1434-82. According to ASTMD-1434-82, permeance, permeability and diffusion are measured by thefollowing formulas: Permeance$\frac{( {{quantity}\quad {of}\quad {gas}} )}{({area}) \times ({time}) \times ( {{press}.\quad {diff}.} )} = {{{{Permeance}({GTR})}/( {{press}.\quad {diff}.} )} = \frac{{cc}.}{( {{sq}.m} )( {24\quad {hr}} )({Pa})}}$Permeability${\frac{( {{quantity}\quad {of}\quad {gas}} ) \times ( {{film}\quad {thick}} )}{({area}) \times ({time})} = {{{{Permeability}({GTR})} \times {( {{film}\quad {thick}} )/( {{press}.\quad {diff}.} )}} = \frac{({cc})({mil})}{( {{sq}.m.} )( {24\quad {hr}} )({Pa})}}}\quad$

[0017] By utilizing the above listed formulas, the gas transmission ratein combination with a constant pressure differential and the film'sthickness, can be utilized to define the movement of gas under specificconditions. In this regard, the preferred gas transmission rate (GTR)for a bladder in an athletic shoe component which seeks to meet therigorous demands of fatigue resistance imposed by heavy and repeatedimpacts has a gas transmission rate (GTR) value of approximately 10.0 orlower and, even more preferably, a (GTR) value of 2.0 or lower, forbladders having an average thickness of approximately 20 mils.

[0018] In addition to the aforementioned, the '029 and '176 patents alsodiscuss problems encountered with previous attempts to use co-laminatedcombinations of plastic material which operate as barriers to oxygen. Inthis regard, the principal concern was the lack of fatigue resistance ofthe barrier layer. As described in the '176 patent, a satisfactoryco-lamination of polyvinylidene chloride (such as Saran®) and a urethaneelastomer would require an intermediate bonding agent. Under such aconstruction, relatively complicated and expensive processing controlssuch as strict time-temperature relationships and the use of heatedplatens and pressures, coupled with a cold press to freeze the materialstogether under pressure would be required. Additionally, using adhesivetie layers or incorporating crystalline components into the flexiblefilm at high enough levels to accomplish a gas transmission rate of 10.0or less, reduces the flexibility of the film.

[0019] Cushioning devices which specifically eliminate adhesive tielayers have been known to separate or de-laminate especially along seamsand edges. Thus, it has been a relatively recent focus of the industryto develop cushioning devices which reduce or eliminate the occurrenceof delamination, ideally without the use of a “tie layer.” In thisregard, the cushioning devices disclosed in co-pending U.S. applicationpatent Ser. Nos. 08/299,286 and 08/299,287 eliminate adhesives tielayers by providing membranes including a first layer of thermoplasticurethane and a second layer including a copolymer of ethylene and vinylalcohol wherein hydrogen bonding occurs over a segment of the membranesbetween the first and second layers. While the cushioning devicesdisclosed in U.S. patent application Ser. No. 08/299,287 and thelaminated flexible barrier membranes of U.S. patent application Ser. No.08/299,286 are believed to offer a significant improvement in the art,still further improvements are offered according to the teachings of thepresent invention.

[0020] It is therefore, a principal object of the present invention toprovide barrier membranes which offer enhanced flexibility, durabilityand resistance to the undesired transmission of fluids therethrough.

[0021] It is another object of the present invention to provide barriermembranes which can essentially be permanently inflated with nitrogen oranother environmentally desirable gas or combination of gases whereinthe barrier membrane provides for a gas transmission rate value of 10.0or less, based on a 20 mils average thickness.

[0022] It is still another object of the present invention to providebarrier membranes and, particularly those employed as cushioning deviceswith improved clarity and consistency.

[0023] It is yet another object of the present invention to providebarrier membranes which can be formed into laminated objects such ascushioning devices or accumulators which resist delamination and do notrequire a tie layer between the barrier layer and the flexible layers.

[0024] It is yet another object of the present invention to providebarrier layers which are reprocessable.

[0025] It is a further object of the present invention to providebarrier membranes which are formable utilizing the various techniquesincluding, but not limited to, blow-molding, tubing, sheet extrusion,vacuum-forming, heat-sealing and RF welding.

[0026] Still another object of the present invention is to providebarrier membranes which prevent gas from escaping along interfacesbetween the layers in laminated embodiments and particularly along seemsvia capillary action.

[0027] It is yet another object of the present invention to provide abarrier membrane which allows for normal footwear processing such asencapsulation within a formable material.

[0028] While the aforementioned objects provide guidance as to possibleapplications for the barrier membranes of the present invention, itshould be recognized by those skilled in the art that the recitedobjects are not intended to be exhaustive or limiting.

SUMMARY OF THE INVENTION

[0029] To achieve the foregoing objects, the present invention providesbarrier membranes which have (1) a desirable level of flexibility (orrigidity); (2) a desirable level of resistance to degradation caused bymoisture; (3) an acceptable level of imperviousness to fluids which canbe in the form of gases, liquids or both depending mainly on theintended use of the product; and (4) are highly resistant todelamination when employed in a multi-layer structure. Regardless of thebarrier membrane embodiment, each barrier membrane in accordance withthe teachings of the present invention includes a barrier layercomprised at least in part of a blend of at least one aliphaticthermoplastic urethane and at least one copolymer of ethylene and vinylalcohol.

[0030] The aliphatic thermoplastic urethanes employed, if notcommercially available, are generally formed as the reaction product of(a) at least one polyester and/or polyether diol; (b) at least onedifunctional extender, and (c) at least one aliphatic isocyanate and/ordiisocyanate, as will be described in greater detail below.Additionally, it may be desirable to utilize a catalyst to activate thereaction and one or more processing aids.

[0031] The term “thermoplastic” as used herein is intended to mean thatthe material is capable of being softened by heating and hardened bycooling through a characteristic temperature range, and as such in thesoftened state can be shaped into various articles under varioustechniques.

[0032] The term “polyester diol” as used herein is intended topreferably mean polymeric polyester diols having a molecular weight(determined by the ASTM D-4274 method) falling in the range of about 300to about 4,000; more preferably from about 400 to about 2,000; and stillmore preferably between about 500 to about 1,500.

[0033] The term “polyether diol” as used herein is intended topreferably mean polymeric polyether diols having a molecular weight(determined by ASTM D-4274 method) falling in the range of about 300 toabout 6,500; more preferably from about 400 to about 4,500; and stillmore preferably between about 500 to about 3,000.

[0034] The term “difunctional extender” is used preferably in thecommonly accepted sense to one skilled in the art and includes glycols,diamines, amino alcohols and the like having a molecular weightgenerally falling in the range of from about 60 to about 300.

[0035] The terms “aliphatic isocyanate” and “aliphatic diisocyanate” asused herein are intended preferably to mean linear aliphatic,cycloaliphatic and hindered aromatic isocyanates and diisocyanates wherethe isocyanate —N— is separated from the benzenoid ring proper by atleast one carbon, and hence, acts to produce light stable or “aliphatic”(poly)urethanes.

[0036] Ideally, the flexible barrier materials utilized in accordancewith the teachings of the present invention should be capable ofcontaining a captive gas for a relatively long period of time. In ahighly preferred embodiment, for example, the barrier membrane shouldnot lose more than about 20% of the initial inflated gas pressure over aperiod of two years. In other words, products inflated initially to asteady state pressure of between 20.0 to 22.0 psi should retain pressurein the range of about 16.0 to 18.0 psi.

[0037] Additionally, the barrier materials utilized should be flexible,relatively soft and compliant and should be highly resistant to fatigueand be capable of being welded to form effective seals typicallyachieved by RF welding or heat sealing. The barrier material should alsohave the ability to withstand high cycle loads without failure,especially when the barrier material utilized has a thickness of betweenabout 5 mils to about 50 mils. Another important characteristic of thebarrier membrane is that they should be processable into various shapesby techniques used in high volume production. Among these techniquesknown in the art are extrusion, blow molding, injection molding, vacuummolding, rotary molding, transfer molding and pressure forming. Thebarrier membranes of the present invention should be preferably formableby extrusion techniques, such as tubing or sheet extrusion, includingextrusion blow molding particularly at sufficiently high temperatures toattain the desired “adhesive” or “chemical” bonding as will be describedin greater detail below. These aforementioned processes should give riseto products whose cross-sectional dimensions can be varied.

[0038] As alluded to above, a significant feature of the barriermembranes of the present invention is the ability under embodimentsformed into products intended to be inflated (such as cushioning devicesfor footwear) to control diffusion of mobile gases through the membraneand to retain the captive gases contained therein. By the presentinvention, not only are super gases usable as captive gases, butnitrogen gas may also be used as a captive gas due to the performance ofthe barrier. The practical effect of providing a barrier membrane forwhich nitrogen gas is a captive gas is significant in terms ofprotection of the earth's ozone and global warming.

[0039] Under the present invention, if the barrier membrane is formedinto a product such as a cushioning device, the membrane may beinitially inflated with nitrogen gas or a mixture of nitrogen gas andone or more super gases or with air. If filled with nitrogen or amixture of nitrogen and one or more super gases, an increment ofpressure increase results from the relatively rapid diffusion of oxygengas into the membrane, since the captive gas is essentially retainedwithin the membrane. This effectively amounts to an increase in pressureof not greater than about 2.5 psi over the initial inflation pressureand results in a relatively modest volume growth of the membrane ofbetween 1 to 5%, depending on the initial pressure. However, if air isused as the inflatant gas, oxygen tends to diffuse out of the membranewhile the nitrogen is retained as the captive gas. In this instance, thediffusion of oxygen out of the membrane and the retention of the captivegas results in an incremental decrease of the steady state pressure overthe initial inflation pressure.

[0040] A further feature of the present invention is the enhancedbonding which occurs between contiguous layers, thus, eliminating theneed for adhesive tie layers. This is generally accomplished bylaminating the first and second layers together using conventionaltechniques and thus, the laminated barrier membranes of the presentinvention are characterized in that significant hydrogen bonding occursbetween a first layer formed from a blend of at least one aliphaticthermoplastic urethane and a copolymer of ethylene and vinyl alcohol,and a second layer of thermoplastic urethane. In addition to theoccurrence of hydrogen bonding, it is theorized that there will alsogenerally be a certain amount of covalent bonding between the first andsecond layers, especially when lesser amounts of the copolymer ofethylene and vinyl alcohol is used in the first layer and thethermoplastic urethanes of both the first and second layers have similarfunctionalities.

[0041] This invention has many other advantages which will be moreapparent from consideration of the various forms and embodiments of thepresent invention. Again, while the embodiments shown in theaccompanying drawings which form a part of the present specification areillustrative of embodiments employing the barrier membranes of thepresent invention, it should be clear that the barrier membranes haveextensive application possibilities. Various exemplary embodiments willnow be described in greater detail for the purpose of illustrating thegeneral principles of the invention, without considering the followingdetailed description in the limiting sense.

BRIEF DESCRIPTION OF THE DRAWINGS

[0042]FIG. 1 is a side elevational view of an athletic shoe inaccordance with the present invention with a portion of the midsolecut-a-way to expose a cross-sectional view;

[0043]FIG. 2 is a bottom elevational view of the athletic shoe of FIG. 1with a portion cut-a-way to expose another cross-sectional view;

[0044]FIG. 3 is a section view taken alone line 3-3 of FIG. 1;

[0045]FIG. 4 is a fragmentary side perspective view of one embodiment ofa tubular-shaped, two-layer cushioning device in accordance with thepresent invention;

[0046]FIG. 5 is a sectional view taken along line 4-4 of FIG. 4;

[0047]FIG. 6 is a fragmentary side perspective view of a secondembodiment of a tubular-shaped, three-layer cushioning device inaccordance with the present invention;

[0048]FIG. 7 is a sectional side view taken along line 6-6 of FIG. 6;

[0049]FIG. 8 is a perspective view of an alternative membrane embodimentaccording to the present invention;

[0050]FIG. 9 is a side view of the membrane illustrated in FIG. 8;

[0051]FIG. 10 is a perspective view of an alternative membraneembodiment according to the present invention;

[0052]FIG. 11 is a side elevational view of an athletic shoe having analternative membrane embodiment according to the present invention;

[0053]FIG. 12 is a perspective view of the membrane illustrated in FIG.11;

[0054]FIG. 13 is a top elevation view of the membrane illustrated inFIGS. 11 and 12;

[0055]FIG. 14 is a side elevation view of an athletic shoe havinganother alternative membrane embodiment according to the presentinvention;

[0056]FIG. 15 is a perspective view of the membrane illustrated in FIG.14;

[0057]FIG. 16 is a top view of the membrane illustrated in FIGS. 14 and15;

[0058]FIG. 17 is a perspective view of an alternative membraneembodiment according to the teachings of the present invention;

[0059]FIG. 18 is a side view of the membrane illustrated in FIG. 17;

[0060]FIG. 19 is a perspective view of an accumulator formed from alaminated membrane according to the teachings of the present invention;

[0061]FIG. 20 is a perspective view of a second accumulator embodimentformed from a laminated membrane according to the teachings of thepresent invention;

[0062]FIG. 21 is a side elevation view of a sheet co-extrusion assembly;

[0063]FIG. 22 is a cross-sectional view of the manifold portion of thesheet co-extrusion assembly of FIG. 21; and

[0064]FIG. 23 is a side elevation view of a tubing co-extrusionassembly.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0065] Referring to FIGS. 1-5, there is shown an athletic shoe,including a sole structure and a cushioning device as one example of aproduct employing a barrier membrane in accordance with the teachings ofthe present invention. The shoe 10 includes a shoe upper 12 to which thesole 14 is attached. The shoe upper 12 can be formed from a variety ofconventional materials including, but not limited to, leathers, vinyls,nylons and other generally woven fibrous materials. Typically, the shoeupper 12 includes reinforcements located around the toe 16, the lacingeyelets 18, the top of the shoe 20 and along the heel area 22. As withmost athletic shoes, the sole 14 extends generally the entire length ofthe shoe 10 from the toe region 20 through the arch region 24 and backto the heel portion 22.

[0066] The sole structure 14 includes one or more selectively permeablebarrier membranes 28 in accordance with the present invention, which arepreferably disposed in the midsole H of the sole structure. By way ofexample, the barrier membranes 28 of the present invention can be formedhaving various geometries such as the plurality of tubular members whichare positioned in a spaced apart, parallel relationship to each otherwithin the heel region 22 of the mid sole 26 as illustrated in FIGS.1-5. The tubular members are sealed to contain an injected captive gas.More specifically, each of the barrier membranes 28 are formed toinclude a barrier layer which permits diffusion of mobile gasestherethrough but which resists or prevents diffusion of the captivegases. These predetermined diffusion properties of the membrane 28 areprovided by an inner barrier layer 30 which is disposed along the innersurface of a thermoplastic outer layer 32. These two membrane layers maybe best seen in FIGS. 4 and 5. As previously noted, the barriermembranes 28 of the present invention can be formed in a variety ofconfigurations or shapes. For example, alternative membranes 28B couldbe formed in the shape of a heel ped as illustrated in FIGS. 8 and 9.Athletic shoes including the heel ped configurations set forth in FIGS.8 and 9 have been used commercially and sold under the trademark AirHealth Walker Plus™ by Nike, Inc. of Beaverton, Oreg. The heel pedconfiguration of FIGS. 8 and 9 is also shown in U.S. Design Pat. No.007,934, filed on Apr. 20, 1993. Similarly, heel peds having a geometrysubstantially similar to the membrane embodiment 28C illustrated in FIG.10 have been used in athletic shoes sold under the trademark AirStructure II™ by Nike, Inc. The heel ped configuration of FIG. 10 isalso shown in U.S. Design Pat. No. 343,504, issued on Jan. 25, 1994. Byway of further example, an alternate membrane 28D illustrated withreference to FIGS. 11-13, is currently used in athletic shoes sold underthe trademarks Air Max²™ and Air Max²CB™, also owned by Nike, Inc. areformable in accordance with the teachings of the present invention. Thismembrane configuration is also shown in U.S. Design Pat. No. 349,804,issued on Aug. 23, 1994, and U.S. Design Pat. No. 350,016 issued on Aug.30, 1994. Yet, another alternative membrane 28E is illustrated withreference to FIGS. 14-16. The membrane 28E is currently utilized inathletic shoes sold under the trademark Air Max™ by Nike, Inc. Thismembrane configuration is also shown in U.S. Design Pat. No. 897,966,filed on Jun. 12, 1992. Still another membrane configuration designatedby reference numeral 28F is illustrated in FIGS. 17 and 18. As should beappreciated by this point, barrier membrane configurations under thepresent invention (whether in the form of a tube, an elongated ped orother such configuration), may either be fully or partially encapsulatedwithin the midsole or out-sole of an article of footwear.

[0067] Referring again to FIGS. 1-5, a barrier membrane 28 in accordancewith teachings of the present invention is provided in the form of acushioning device. As shown, the membrane 28 has a composite structureincluding an outer layer 32 formed of a flexible resilient elastomericmaterial which preferably is resistant to expansion beyond apredetermined maximum volume for the membrane when subjected to gaseouspressure. The membrane 28 also includes an inner layer 30 formed of abarrier material which allows for controlled diffusion pumping orself-pressurization.

[0068] The outer layer 32 preferably is formed of a material orcombination of materials which offer superior heat sealing properties,flexural fatigue strength, a suitable modulus of elasticity, tensile andtear strength and abrasion resistance. Among the available materialswhich offer these characteristics, it has been found that thermoplasticelastomers of the urethane variety, otherwise referred to herein asthermoplastic urethanes or simply TPU's, are highly preferred because oftheir excellent processibility.

[0069] Among the numerous thermoplastic urethanes which are useful informing the outer layer 32, urethanes such as PELLETHANE™ 2355-85ATP and2355-95AE (trademarked products of the Dow Chemical Company of Midland,Mich.), ELASTOLLAN® (a registered trademark of the BASF Corporation) andESTANE® (a registered trademark of the B. F. Goodrich Co.), all of whichare either ester or ether based, have proven to be particularly useful.Still other thermoplastic urethanes based on polyesters, polyethers,polycaprolactone and polycarbonate macroglycols can be employed. Ingeneral, the thermoplastic urethane(s) employed to form the outer layer32 will be aromatic in nature.

[0070] The inner layer 30, which is the main barrier constituentprimarily responsible for controlling gas permeation, is made from acombination or blend of one or more aliphatic thermoplastic urethanesand one or more copolymers of ethylene and vinyl alcohol. The aliphaticthermoplastic urethanes employed in the inner barrier layer, if notcommercially available, are generally formed by the reaction product ofat least one of each of the following: (a) polyester and/or polyetherdiol; (b) difunctional extender; (c) aliphatic isocyanates and/ordiisocyanates; and (d) optionally, a catalyst.

[0071] Among the numerous polyester diols (otherwise referred to hereinas polyester polyols) which are considered to be useful in accordancewith the teachings of the present invention, those which are obtained bythe esterification of an aliphatic or aromatic dibasic acid or anhydridewith a glycol are considered to be particularly useful. Preferably, theglycol is employed in excess of the stoichiometric proportion withrespect to the acid or anhydride in order to ensure that the polyestersare hydroxyl-terminated. As previously noted, ideally any polyesterdiols employed will have a molecular weight ranging from about 300 toabout 4,000, more preferably from about 400 to about 2,000, and stillmore preferably from about 500 to about 1,500, as calculated accordingto the procedure set forth in ASTM D-4274.

[0072] Representative dicarboxylic acids (or their anhydrides) employedin the preparation of the polyester diols are adipic, succinic, pimelic,suberic, azelaic, sebacic, terephthalic, phthalic, and the like acids ortheir anhydrides or mixture of two or more of said acids or anhydrides.Adipic acid is the preferred acid. Representative glycols employed inthe preparation of the polyalkylene ester diols are the straight chainaliphatic glycols containing from 2 to 10 carbon atoms, inclusive, suchas ethylene glycol, propane-1,3-diol, butane-1,4-diol,2-butene-1,4-diol, hexane-1,6-diol, octane-1,8-diol, decane-1,10-diol,and the like, or mixtures of two or more such glycols.

[0073] Representative of glycols employed in the preparation of thepolyoxyalkylene ester diols are diethylene glycol, dipropylene glycol,and the like.

[0074] Representative of the polyoxyalkanoyl diols are thepolycaprolactone diols which are prepared by polymerizing theappropriate caprolactone with the appropriate difunctional initiator,such as an aliphatic glycol or an alkanolamine, and the like. For afurther understanding of the procedures and products for obtaining thevarious polyol esters, reference can be made to U.S. Pat. No.2,9414,556, which is hereby expressly incorporated by reference.

[0075] Preferred species of polyester diols include polyethyleneadipate, polypropylene adipate, and polybutylene adipate.

[0076] Among the numerous polyether diols (otherwise referred to hereinas polyether polyols) which can be employed in accordance with theteachings of the present invention, those including hydroxyl(polyalkylene oxides), or polyether macroglycols are generallypreferred. Ideally, the polyether macroglycols employed are linearhydroxyl-terminated compounds having ether linkages as the major linkagejoining carbon atoms. The molecular weights may vary from between about300 to about 6,500, more preferably from about 400 to about 4,500, andstill more preferably from about 500 to about 3,000, also based on ASTMD-4274. The hydroxyl (polyalkylene oxides) such as hydroxyl poly(tetramethylene oxide), hydroxyl poly (trimethylene oxide), hydroxylpoly (hexamethylene oxide), hydroxyl poly (ethylene oxide) and the likeof the formula HO[(CH₂)_(n)O]_(x)H wherein n is a number from 2 to 6 andx is an integer, and alkyl substituted types such as hydroxyl poly(1,2-propylene oxide); tetrahydrofuran and ethylene oxide copolyethersare all considered to be useful examples.

[0077] Among the difunctional extenders employed in accordance with theteachings of the present inventions are those generally selected fromthe group consisting of aliphatic extenders including ethylene glycol,1,3-propylene glycol, 1,2-propylene glycol, 1,4-butanediol,1,2-hexanediol, neopentyl glycol, and the like; and dihydroxyalkylatedaromatic compounds such as the bis (2-hydroxyethyl) ethers ofhydroquinone and resorcinol; p-xylene-α,α′-diol; the bis(2-hydroxyethyl) ether of p-xylene-α,α′-diol; m-xylene-α,α′-diol and thebis (2-hydroxyethyl) ether thereof. Illustrative of diamine extendersare aromatic diamines such as p-phenylenediamine, m-phenylenediamine,benzidine, 4,4′-methylenedianiline, 4,4′-methylenibis (2-chloroaniline)and the like. Illustrative of amino alcohols are ethanolamine,propanolamine, butanolamine, and the like.

[0078] Preferred extenders include ethylene glycol, 1,3-propyleneglycol, 1,4-butanediol, 1,2-hexanediol, 1,6 hexanediol and the like.

[0079] Generally, the ratio of polyol (whether ester or ether based) toextender can be varied within a relatively wide range depending largelyon the desired hardness of the final polyurethane elastomer. As such,the equivalent proportion of polyester and/or polyether diol to extendershould be within the range of 1:1 to 1:12 and, more preferably, from 1:1to 1:8.

[0080] Among the aliphatic isocyanates and, more particularly, aliphaticdiisocyanates employed those including isophorone diisocyanate (IPDI),methylene bis 4-cyclohexyl isocyanate, cyclohexyl diisocyanate (CHDI),hexamethylene diisocyanate (HDI), m-tetramethyl xylene diisocyanate(m-TMXDI), p-tetramethyl xylene diisocyanate (P-TMXDI) and xylylenediisocyanate (XDI) are considered to be particularly useful. Generally,the diisocyanate(s) employed are proportioned such that the overallratio of equivalents of isocyanate to equivalents of active hydrogencontaining materials is within the range of 0.95:1 to 1.10:1, andpreferably 0.98:1 to 1.04:1.

[0081] As previously noted, it is frequently desirable to include acatalyst in the reaction mixture to prepare the compositions of thepresent invention. Any of the catalysts conventionally employed in theart to catalyze the reaction of an isocyanate with a reactive hydrogencontaining compound can be employed for this purpose; see, for example,Saunders et al., Polyurethanes, Chemistry and Technology, Part I,Interscience, New York, 1963, pages 228-232; see also, Britain et al.,J. Applied Polymer Science, 4, 207-211, 1960. Such catalysts includeorganic and inorganic acid salts of, and organometallic derivatives of,bismuth, lead, tin, iron, antimony, uranium, cadmium, cobalt, thorium,aluminum, mercury, zinc, nickel, cerium, molybdenum, vanadium, copper,manganese and zirconium, as well as phosphines and tertiary organicamines. Representative organotin catalysts are stannous octoate,stannous oleate, dibutyltin dioctoate, dibutyltin dilaurate, and thelike. Representative tertiary organic amine catalysts are triethylamine,triethylenediamine, N₁N₁N′₁N′-tetramethylethylenediamine,N₁N₁N′₁N′-tetraethylethylenediamine, N-methyl-morpholine,N-ethylmorpholine, N₁N₁N′₁N′-tetramethylguanidine, andN₁N₁N′₁N′-tetramethyl-1,3-butanediamine.

[0082] Regardless of the catalyst(s) which is utilized, if any, theweight percentage of such material is typically less than one half ofone percent by weight (0.5 wt. %) based on the total weight of thealiphatic thermoplastic urethane reaction mixture.

[0083] As noted, it is also possible to employ various commerciallyavailable aliphatic thermoplastic urethanes such as those marketed underthe tradename MORTHANE® which is a registered trademark of MortonInternational of Chicago, Ill. Among the various commercially availablepolyester based aliphatic thermoplastic urethanes which are consideredto be useful, those sold as MORTHANE PN03-204, PN03-214 and PN3429-100are believed to be particularly useful. Still other commerciallyavailable polyester based aliphatic thermoplastic urethanes which can beemployed include those sold under the trademark TEXIN™ by BAYER A G(America) of Pittsburgh, Pa. An example of the TEXINT™ polyester basedaliphatic thermoplastic urethanes considered to be useful is that soldas TEXIN DP7-3013.

[0084] As for the aliphatic polyether based thermoplastic urethanes,those sold as MORTHANE PE192-100, PE193-100 and PE194-100 are believedto be particularly useful. Still other commercially available polyetherbased aliphatic thermoplastic urethanes include those sold under thetrademark TECOFLEX™ by Thermedics, Inc., of Woburn, Mass. Among theuseful examples of TECOFLEX™ polyether based aliphatic urethanes arethose sold under the trade designations TECOFLEX EG-80A, EG-85A, EG-93A,EG-60D, EG-65D and EG-72D. Further, a commercially available polyetherbased aliphatic urethanes known as DP7-3005, DP7-3006 and DP7-3007available from Bayer A G (America) are also considered useful.

[0085] Regardless of which aliphatic thermoplastic urethane is employed(i.e. reaction product or commercially available product), the blendedbarrier layer 30 will generally include up to 50.0 wt. % aliphaticthermoplastic urethane but, more preferably, will include between about1.0 wt. % to about 30.0 wt. % aliphatic thermoplastic urethanes. Underhighly preferred embodiments, the aliphatic thermoplastic urethaneconstituency of the barrier layer 30 will be present in the range ofbetween about 5.0 wt. % to about 25.0 wt. %.

[0086] Among the copolymers of ethylene and vinyl alcohol employed inthe blend forming the barrier layer 30 those including commerciallyavailable products such as SOARNOL™ which is available from the NipponGohsei Co., Ltd. (U.S.A.) of New York, N.Y., and EVAL™ which isavailable from Eval Company of America, Lisle, Ill. have proven to beuseful. Highly preferred commercially available copolymers of ethyleneand vinyl alcohol such as EVAL® LCF101A will typically have an averageethylene content of between about 25 mol % to about 48 mol %. Ingeneral, ethylene contents within this range give rise to strongerbonding between the respective layers of thermoplastic urethane andethylene-vinyl alcohol copolymers.

[0087] With regard to the use of so-called processing aids, minoramounts of antioxidants, UV stabilizers, mold release agents andnon-sticking agents as are known in the art may be employed wherein thetotal constituency of all “processing aids” is generally less than 3.0wt. %.

[0088] For certain embodiments, it may also be useful to include arelatively small amount of at least one aromatic thermoplastic urethanein the blended barrier layer 30 as a viscosity modifier. Under thoseembodiments employing at least one aromatic thermoplastic urethane, thetotal amount will generally be 3 wt. % or less based on a 100 wt. %constituency of the barrier layer. Thus, the composition of the blendedbarrier layer can be summarized as including: (1) 50 wt. % to about 97wt. % of at least one copolymer of ethylene and vinyl alcohol; (2) 3 wt.% to about 50 wt. % of at least one aliphatic thermoplastic urethane;and (3) up to about 3 wt. % of one or more aromatic thermoplasticurethanes, wherein the total constituency of the barrier layer is equalto 100 wt. %. The aromatic thermoplastic urethanes are also selectedfrom the group consisting of polyester, polyether, polycaprolactone,polyoxypropylene and polycarbonate macroglycol based materials andmixtures thereof.

[0089] As previously noted, the barrier membranes as disclosed hereincan be formed by various processing techniques including but not limitedto extrusion, blow molding, injection molding, vacuum molding and heatsealing or RF welding of tubing and sheet extruded film materials.Preferably, all will be described in greater detail below, the membranesof the present invention are made from films formed by co-extruding theouter layer of thermoplastic urethane material and the inner layer ofthe blended aliphatic thermoplastic urethane and copolymer of ethyleneand vinyl alcohol together to effectively produce multi-layered filmmaterials with the resulting barrier membranes produced from thismaterial. Subsequently, after forming the multi-layered film materials,the film materials are heat sealed or welded by RF welding to form theinflatable barrier membranes which have the characteristics of both highflexibility and diffusion pumping capabilities.

[0090] Referring to FIGS. 6 and 7, an alternative barrier membraneembodiment 28A in the form of an elongated tubular shaped multi-layeredcomponent is illustrated. The modified barrier membrane 28A isessentially the same as the composite structure illustrated in FIGS. 1-5except that a third layer 34 is provided contiguously along the innersurface of the barrier layer 30, such that the barrier layer 30 issandwiched between the outer layer 32 and innermost layer 34. Theinnermost layer 34 is also preferably made from a thermoplastic urethanebased material to add further protection against moisture coming incontact with the barrier layer 30. In addition to the benefits ofenhanced protection against degradation of the barrier layer 30, layer34 also tends to assist in providing for high quality welds which allowfor the three-dimensional shapes of the cushioning devices.

[0091] The cushioning devices shown in FIGS. 1-7 are preferablyfabricated from multi-layered extruded tubes. Lengths of the coextrudedtubing ranging from one foot to coils of up to 5 feet, are inflated to adesired initial inflation pressure ranging from 0 psi ambient to 100psi, preferably in the range of 5 to 50 psi, with the captive gaspreferably being nitrogen. Sections of the tubing are RF welded or heatsealed to the desired lengths. The individual cushioning devicesproduced are then separated by cutting through the welded areas betweenadjacent cushioning devices. It should also be noted that the cushioningdevices can be fabricated with so-called lay flat extruded tubing as isknown in the art whereby the internal geometry is welded into the tube.

[0092] As the blended first layer including one or more aliphaticurethanes and one or more copolymers of ethylene and vinyl alcohol andthe second layer including thermoplastic urethane advance to the exitend of the extruder through individual flow channels, once they near thedie-lip exit, the melt streams are combined and arranged to floattogether in layers typically moving in laminar flow as they enter thedie body. Ideally, the materials are combined at a temperature ofbetween about 300° F. to about 450° F. and a pressure of at least about200 psi to obtain optimal wetting for maximum adhesion between thecontiguous portions of the layers 30, 32 and 34 respectively.

[0093] The membrane 28A as shown in FIGS. 6 and 7 comprises three layersincluding a first layer of barrier material 30 sandwiched between secondand third layers 32 and 34, respectively, of thermoplastic urethane. Ina highly preferred embodiment, the two thermoplastic urethane layers andthe blended barrier layer of one or more aliphatic urethanes and one ormore copolymers of ethylene and vinyl alcohol are coextruded attemperatures sufficient to cause a reactive contact in the form ofhydrogen bonding to occur along at least a predetermined segment of thebarrier membrane, thus eliminating the need for an intermediate adhesiveor bonding layer.

[0094] To this end, it is believed that significant bonding occurs asthe result of available hydrogen molecules being donated by the vinylalcohol groups of the ethylene-vinyl alcohol co-polymer along the lengthof the laminated membrane and hydroxyl and urethane carbonyl groups, orsimply the available polar groups of aliphatic thermoplastic urethane.

[0095] The preferred compositions and methods of the present inventionrely exclusively on the inherent properties of the thermoplasticurethane of the second and third layers and the blended barrier layerincluding aliphatic thermoplastic urethane and one or more copolymers ofethylene and vinyl alcohol when brought into contact according to themethods of the present invention for adhesion.

[0096] The theoretical chemical reaction which forms a surface bondbetween layers 32 and 34 with layer 30 across substantially the entireintended contact surface area of the membrane 28A can be summarized asfollows:

[0097] and R′ is a short chain diol such as (CH₂)₄

[0098] In addition to the aforementioned theoretical hydrogen bonding,to a more limited extent, it is believed that a certain amount ofcovalent bonds are formed between the second and third layers 32 and 34,respectively, with the first barrier layer 30. Still other factors suchas orientation forces and induction forces, otherwise known as van derWaals forces, which result from London forces existing between any twomolecules and dipole-dipole forces which are present between polarmolecules are believed to contribute to the bond strength betweencontiguous layers of thermoplastic urethane and the main barrier layer.

[0099] The hydrogen bonding between layers of thermoplastic urethane andthe barrier layer including one or more aliphatic urethanes and one ormore copolymers of ethylene and vinyl alcohol of the present inventionis in contrast to prior art embodiments which, failing to recognize theexistence and/or potential of such bonding, typically have used adhesivetie-layers such as Bynel®, for example, to improve and maintain thebonding between the various layers of thermoplastic urethane andethylene vinyl alcohol.

[0100] It should also be noted that fillers such as non-polar polymericmaterials and inorganic fillers or extenders such as talc, silica, mica,etc., tend to negatively effect the bonding capacity of thethermoplastic urethane and the blended layer including at least onealiphatic urethane and at least one copolymer of ethylene and vinylalcohol. Thus, the use of fillers in processing the layers 30, 32 and 34should be extremely limited, if used at all.

[0101] Referring to FIGS. 12-16, barrier membranes in the form of airbladders, otherwise referred to herein as cushioning devices, which arefabricated by blow molding are shown. To form the air bladders, parisonsof two layer, or preferably three layer film are first coextruded asillustrated in FIGS. 21-23, and thereafter, the parisons are blown andformed using conventional blow molding techniques. The resultingbladders, shown best in FIGS. 12 and 15 are then inflated with thedesired captive gas to the preferred initial inflation pressure and thenthe inflation port (e.g. inflation port 38) is sealed by RF welding.

[0102] Another air bladder embodiment formed from the barrier membranesdescribed herein is shown in FIGS. 8-10. Sheets or films of coextrudedtwo layer, or preferably three layer film are first formed, with thethickness range of the coextruded sheets or films generally beingbetween 0.5 mils to 10 mils for the barrier layer 30 and between 5 milsto about 100 mils for the thermoplastic urethane layers 32 and 34,respectively. Two sheets of the multi-layer film are placed on top ofeach other and welded together along selected points using conventionalheat sealing techniques or RF welding techniques. The uninflated bladderis then inflated through a formed inflation port to the desired initialinflation pressure which ranges from 0 psi ambient to 100 psi, andpreferably 5 to 50 psi. As previously noted, the preferred captive gasis nitrogen.

[0103] Still another air bladder embodiment formed from a barriermembrane of the present invention is shown in FIGS. 17 and 18. The airbladder is fabricated by forming co-extruded two and three layer tubinghaving a thickness range of the co-extruded tubing wall, i.e. across-section through all layers, of between 0.5 mils to about 10 milsfor the barrier layer 30 and between about 5 mils to about 100 mils forthe thermoplastic urethane layers 32 and 34, respectively. The tubing iscollapsed to a lay flat configuration and the opposite walls are weldedtogether at selected points and at each end using conventional heatsealing techniques or RF welding. The bladder is then inflated throughthe formed inflation port 38 to the desired inflation pressure whichranges from 0 psi ambient to 100 psi, and preferably from 5 to 50 psi,with the preferred captive gas being nitrogen.

[0104] The various products described in FIGS. 1-18 are designed to beused as midsoles for articles of footwear, and particularly in athleticshoes. In such applications, the inflatable membranes may be used in anyone of several different embodiments including: (1) completelyencapsulated in a suitable midsole foam; (2) encapsulated only on thetop portion of the unit to fill-in and smooth-out the uneven surfacesfor added comfort under the foot; (3) encapsulated on the bottom portionto assist attachment of the out-sole; (4) encapsulated on the top andbottom portions but exposing the perimeter sides for cosmetic andmarketing reasons; (5) encapsulated on the top and bottom portions butexposing only selected portions of the sides of the unit; (6)encapsulated on the top portion by a molded “Footbed”; and (7) used withno encapsulation foam whatsoever.

[0105] In addition to employing the barrier membranes of the presentinvention as cushioning devices or air bladders as described above,still another highly desirable application for the barrier membranes ofthe present invention is for accumulators as illustrated in FIGS. 19 and20.

[0106] Referring to FIGS. 19 and 20, there are shown two alternativeaccumulator embodiments formed from the barrier membrane materials ofthe present invention. According to FIG. 19, a bladder in the form of ahydraulic accumulator which is used for vehicle suspension systems,vehicle brake systems, industrial hydraulic accumulators or for anyaccumulators having differential pressures between two potentiallydissimilar fluid media is illustrated. The bladder 124 separates thehydraulic accumulator into two chambers or compartments, one of whichcontains a gas such as nitrogen and the other one of which contains aliquid. Bladder 124 includes an annular collar 126 and a flexiblepartition 128. Annular collar 126 is adapted to be securedcircumferentially to the interior surface of the spherical accumulatorsuch that partition 128 divides the accumulator into two separatechambers. Flexible partition 128 moves generally diametrically withinthe spherical accumulator and its position at any given time isdependant upon the pressure of the gas on one side in conjunction withthe pressure of the liquid on the opposite side.

[0107] By way of further example, FIG. 20 illustrates a productmanufactured using a combination of the barrier membrane 110, whichincludes a barrier layer 114 formed from a combination or blend of oneor more aliphatic thermoplastic urethanes and one or more copolymers ofethylene and vinyl alcohol, is disposed intermittently between an innerlayer 112 and an outer layer 116 of thermoplastic urethane. It may bedesirable to utilize these so-called intermittent constructions undercircumstances where the delamination potential along certain segments ofa product is generally relatively high. One such location is along theannular collar 128 of bladder or diaphragm for hydraulic accumulators.Thus, it should be recognized that the barrier membranes 110 describedherein can include segments which do not include one or more layers ofthe blend of at least one aliphatic thermoplastic urethane and at leastone copolymer of ethylene and vinyl alcohol.

[0108] Preferably, the aliphatic thermoplastic polyurethane and ethylenevinyl alcohol copolymer employed are not modified in an effort to createcross-linking or conventional covalent bonding between the two layers;nor are any tie-layers or adhesive employed. The preferred compositionsand methods of the present invention rely exclusively on the inherentproperties of the aliphatic thermoplastic urethane and copolymer ofethylene and vinyl alcohol when brought into reactive contact accordingto the methods of the present invention, e.g., to maximize and relyprimarily upon hydrogen bonding occurring between the respective layers.

[0109] To form the barrier membranes 110 according to the teachings ofthe present invention, a number of different processes can be used,including but not limited to, coextrusion blow molding utilizingcontinuous extrusion, intermittent extrusion utilizing (1) reciprocatingscrew systems, (2) ram accumulator-type systems; (3) and accumulatorhead systems, coinjection stretch blow molding, or co-extruded sheet,blown film, tubing or profiles. It has been found that multi-layerprocesses such as tubing, sheet and film extrusion, blow moldingutilizing co-extrusions give rise to products which appear todemonstrate the desired significant hydrogen bonding between therespective layers of thermoplastic urethane and the barrier layer(s)including a blend of aliphatic thermoplastic urethane and copolymers ofethylene and vinyl alcohol. To form a product such as a hydraulicaccumulator via a multi-layer process, such as blow molding,commercially available blow molding machines such as a Bekum BM502utilizing a co-extrusion head model no. BKB95-3B1 (not shown) or a KrupKEB-5 utilizing a model no. VW60/35 co-extrusion head (not shown) can beutilized.

[0110] A brief description of multi-layer processing techniques will nowbe provided. Initially, the resinous materials (namely the thermoplasticurethanes and the barrier material including a blend of at least onealiphatic thermoplastic urethane and at least one copolymer of ethyleneand vinyl alcohol) are first dried to the manufacturer's specification(if necessary) and thereafter are fed to an extruder. Typically, thematerials are fed into the extruders according to the order in which thelayers are to be arranged (for example TPU in an outside extruder, theblend of aliphatic TPU and EVOH in a middle extruder and TPU in insideextruder). The extruder heat profile is set for the best processing ofthe individual materials. However, it is suggested that no more than a20° F. difference be present at the exit point of each extruder. As thematerial is forced forward in each extruder the heat profile is set toachieve the best molten mass. The heat profile would typically be setfor between 300° F. to about 450° F. with the feed zone being the lowestset point and all other set points gradually increasing in increments ofapproximately 10° F. until the desired melt is achieved. Once leavingthe extruders a section of pipes is sometimes used to direct thematerial to the multi-layered head (i.e. three or more heads). It is atthis point that any adjustments for differences in heat be addressed.The pumping action of the extruders not only forces the material intothe individual head channels or flow paths but also determines thethickness of each layer. As an example, if the first extruder has a 60mm diameter, the second has an extruder 35 mm diameter and the thirdextruder has a 35 mm diameter, the speed required to produce a 1.3 literbladder or diaphragm requiring 2 mm for the outside layer of TPU, 3 milsfor the barrier layer and 2 mm for the inside layer of TPU isapproximately a cycle time of 26 seconds. The first extruder would havea screw speed of about 10 rpm's, the second extruder would have a screwspeed of about 5 rpm's and the third extruder would have a screw speedof about 30 rpm. Once entering the head channels or flow paths, the heatwould normally be held constant or be decreased to adjust for the meltstrength of the materials. The individual head channels or flow pathskeep separate the molten masses while directing them downward and intothe shape of a parison.

[0111] Just prior to entering the lower die or bushing and the lowermandrel, the material head channels or flow paths are brought togetherunder the pressure created by the now unitary flow path surface area,the gap between the lower bushing and mandril and the pressure on theindividual layers from the respective extruders. This pressure must beat least 200 psi and is normally, under the conditions described, inexcess of 800 psi. At the point where the materials come together oneparison is now formed that is a laminate made up of the three layersincluding a first layer including a blend of at least one aliphaticthermoplastic urethane and at least one copolymer of ethylene and vinylalcohol, and a second and third layers of thermoplastic urethanedisposed along opposite sides of the first layer. The upper limit of thepressure is essentially only constrained by the physical strength of thehead. After exiting the head, the laminate is closed on each end by twomold halves and a gas such as air is injected into the mold forcing thelaminated parison to blow up against the mold and be held in thisfashion until sufficient cooling has taken place (i.e. approximately 16seconds for the aforementioned sample), at which point the gas isexhausted. The part is then removed from the mold and further coolingoccurs to allow for the part to be de-flashed or further processed assome parts may require. As should now be understood by those skilled inthe art, the layers must be held separate until fully melted andpreformed into a hollow tube at which time they are bonded together asdescribed under heat and pressure.

[0112] As those skilled in the plastic forming industry will recognize,the three major components of a blow molding machine, namely theextruders, die heads and mold clamps, come in a number of differentsizes and arrangements to accommodate the consumer production rateschedule and size requirements. Thus, the above described exemplaryprocess can be modified.

[0113] By way of further example, a preferred multi-layer process knownas sheet co-extrusion will now be described in greater detail. Sheetco-extrusion involves an extrusion technique for the simultaneousextrusion of two or more polymers through a single die where thepolymers are joined together such that they form distinct, well bondedlayers forming a single extruded product. According to the presentinvention, typical layer structures are defined as follows:

[0114] A-B

[0115] Two distinct layers consisting of two resins.

[0116] A-B-A

[0117] Three distinct layers consisting of two or three resins.

[0118] A-B-A-B-A

[0119] Five distinct layers consisting of two, three, four or fiveresins.

[0120] wherein A=a layer of thermoplastic urethane; and B=at least onelayer formed from a resin including a blend of at least one aliphaticthermoplastic urethane and at least one copolymer of ethylene and vinylalcohol.

[0121] The equipment required to produce co-extruded sheet consists ofone extruder for each type of resin which are connected to aco-extrusion feed block such as that shown in FIGS. 21 and 23, which arecommercially available from a number of different sources including theCloreon Company of Orange, Tex. and Production Components, Inc. of EauClaire, Wis., among others.

[0122] The co-extrusion feed block 150 shown in FIG. 21 consists ofthree sections. The first section 152 is the feed port section whichconnects to the individual extruders and ports the individual roundstreams of resin to the programming section 154. The programming section154 then reforms each stream of resin into a rectangular shape the sizeof which is in proportion to the individual desired layer thickness. Thetransition section 156 combines the separate individual rectangularlayers into one square port. The melt temperature of the TPU A layersshould be between about 300° F. to about 450° F. To optimize adhesionbetween the TPU A layers and the blended aliphatic TPU and EVOHcopolymer B layer(s), the actual temperature of each melt stream shouldbe set such that the viscosities of each melt stream closely match. Thecombined laminar melt streams are then formed into a single rectangularextruded melt in the sheet die 158 which preferably has a “coat hanger”design as shown in FIG. 22 which is now commonly used in the plasticsforming industry. Thereafter the extrudate can be cooled utilizingrollers 160 forming a rigid sheet by either the casting or calendaringprocess.

[0123] Similar to sheet extrusion, the equipment required to produceco-extruded tubing also consists of one extruder for each type of resinwith each extruder being connected to a common multi-manifolded tubingdie. The polymer melt from each extruder enters a die manifold such asthe one illustrated in FIG. 23 which is commercially available from anumber of different sources including Canterberry Engineering, Inc. ofAtlanta, Ga. and Genca Corporation of Clearwater, Fla. The polymers flowin separate circular flow channels 172A and 172B for the thermoplasticurethane and the blended aliphatic thermoplastic urethane and copolymerof ethylene and vinyl alcohol, respectively. The flow channels are thenshaped into a circular annulus the size of which is proportional to thedesired thickness for each layer. The individual melts are then combinedto form one common melt stream just prior to the die entrance 174. Themelt then flows through a channel 176 formed by the annulus between theouter surface 178 of a cylindrical mandrel 180 and the inner surface 182of a cylindrical die shell 184. The tubular shaped extrudate exits thedie shell and then can be cooled into the shape of a tube by manyconventional pipe or tubing calibration methods. While a two componenttube has been shown in FIG. 23 it should be understood by those skilledin the art that additional layers can be added through separate flowchannels.

[0124] Regardless of the plastic forming process used, it is ofparamount importance that a consistent melt of the resinousthermoplastic urethane, and blended aliphatic thermoplastic urethane andcopolymer of ethylene vinyl alcohol are obtained to accomplish thedesired extensive hydrogen bonding therebetween across the intendedlength or segment of the laminated product. Thus, the multi-layerprocesses utilized should be carried out at maintained temperatures offrom about 300° F. to about 450° F. for the thermoplastic urethanes andthe blend of aliphatic thermoplastic urethane and ethylene vinyl alcoholcopolymer. Furthermore, it is important to maintain sufficient pressureof at least 200 psi at the point where the layers are joined andhydrogen bonding occurs for a sufficient amount of the hydrogen bondingto be maintained.

[0125] As previously noted, in addition to the excellent bonding whichis achieved for the laminated barrier membrane embodiments of thepresent invention, another objective, especially with regard to barriermembranes employed in extended life applications such as in cushioningdevices for footwear, is to provide barrier membranes which are capableof retaining captive gases for extended periods of time. In general,barrier membranes which offer gas transmission rate values of 10.0 orless for a 20 mils thickness as measured according to the proceduresdesignated at ASTM D-1434-82 are acceptable candidates for extended lifeapplications.

[0126] To analyze for gas transmission rates, Sample 1, as set forth inTable I below, was prepared by extruding TPU on a line consisting of asingle screw extruder used in association with a three roll stack andwinder to form a sheet having an average thickness of approximately 20mils. After preparing blends of EVOH copolymer and aliphatic TPUutilizing a single screw extruder, Samples 2, 3 and 5 were prepared bycoextruding the samples on a line employing three KILLION one inchextruders which fed the TPU layers and barrier layer separately to afeed block heated to a temperature of between 300° F.-450° F. whichbrought the materials together under pressure. Thereafter, thecoextruder sheet was extruded downward onto a smooth steel chill rolland pressed through a nip at low pressure. Sample 4 was prepared byinitially extruding a barrier layer to an average thickness ofapproximately 3 mils. Thereafter, a first TPU layer having an averagethickness of approximately 8.5 mils was extrusion coated along one sideof the barrier layer by feeding the barrier layer into the nip betweentwo steel rolls which are simultaneously fed with molten TPU from thesingle screw extruder. Finally, a second layer of TPU having an averagethickness of approximately 8.5 mils was extrusion coated to the otherside of the barrier layer in the same manner.

[0127] With all samples prepared, gas transmission rates were calculatedfor each sample in accordance with the procedures set forth in ASTMD-1434-82.

[0128] As illustrated in Table I below, Sample 2 offered slightly bettergas transmission rate results than those of Samples 3 and 4, however thelaminates of Samples 3 and 4 not only offer very good resistance toundesired gas permeation, but are also believed to be more resistant todelamination. TABLE I Sample # Composition GTR (cc/m²× atm × day) 1(Control) TPU 29.0 2 TPU/EVOH/TPU 0.79 3 TPU/90 wt. % EVOH-10 1.62 wt. %ATPU/TPU 4 TPU/80 wt. % EVOH-20 1.14 wt. % ATPU/TPU 5 TPU/50 wt. %EVOH-50 14.01 wt. % ATPU/TPU

[0129] From an applicability standpoint, the barrier membranecompositions illustrated in Samples 3 and 4 are considered to be thebest available for use in products such as cushioning devices forfootwear, where the membrane must be durable, flexible, readilyprocessable, resistant to environmental degradation and offer excellentgas transmission controls.

[0130] While the above detailed description describes the preferredembodiment of the present invention, it should be understood that thepresent invention is susceptible to modification, variation andalteration without deviating from the scope and fair meaning of thesubjoined claims.

What is claimed is:
 1. A barrier membrane having improved resistance toundesired gas permeation, comprising: a first layer including acombination of at least one aliphatic thermoplastic urethane and acopolymer of ethylene and vinyl alcohol; and a second layer including athermoplastic urethane; said membrane being characterized in thatreactive contact in the form of hydrogen bonding occurs along a segmentof the membrane between the first and second layers.
 2. The barriermembrane according to claim 1, wherein said first layer includes up toabout 50 wt. % of aliphatic thermoplastic urethane.
 3. The barriermembrane according to claim 2, wherein said first layer includes betweenabout 1 wt. % to about 30 wt. % of aliphatic thermoplastic urethane. 4.The barrier membrane according to claim 3, wherein said first layerincludes between about 5 wt. % to about 25 wt. % of aliphaticthermoplastic urethane.
 5. The barrier membrane according to claim 1,wherein said copolymer of ethylene vinyl and alcohol is selected fromthe group consisting of copolymers including an ethylene content ofbetween about 25 mol. % to about 48 mol. %.
 6. The barrier membraneaccording to claim 1, wherein the aliphatic thermoplastic urethane ofsaid first layer includes at least one polyester based urethane.
 7. Thebarrier membrane according to claim 1, wherein said second layer ofthermoplastic urethane is selected from the group consisting ofpolyester, polyether, polycaprolactone, polyoxypropylene andpolycarbonate macroglycol based materials and mixtures thereof.
 8. Thebarrier membrane according to claim 1, wherein said first layerincluding a blend of aliphatic thermoplastic urethane and a copolymer ofethylene and vinyl alcohol has an average thickness of between about 0.5mils to about 10 mils and said second layer including thermoplasticurethane has an average thickness of between about 5 mils to about 100mils.
 9. The barrier membrane according to claim 1, wherein said secondlayer also includes an aromatic urethane.
 10. The barrier membraneaccording to claim 1, wherein said first layer includes: (a) 50 wt. % toabout 97 wt. % of at least one ethylene and vinyl alcohol copolymer; (b)3 wt. % to about 50 wt. % of at least one aliphatic thermoplasticurethane; and (c) up to about 3.0 wt. % of one or more aromaticurethanes; wherein the total constituency of said first layer is equalto 100.0 wt. %.
 11. The barrier membrane according to claim 1, furthercomprising a third layer including a thermoplastic urethane.
 12. Thebarrier membrane according to claim 3, wherein said first layerincluding a blend of at least one aliphatic thermoplastic urethane and acopolymer of ethylene and vinyl alcohol has an average thickness ofbetween about 0.5 mils to about 10 mils and said second and third layersincluding thermoplastic urethanes have an average thickness of betweenabout 5 mils to about 100 mils.
 13. A barrier membrane having animproved resistance to undesired gas permeation, comprising: a firstlayer including a combination of at least one aliphatic thermoplasticurethane and one or more copolymers of ethylene and vinyl alcohol; asecond layer including a thermoplastic urethane; and a third layerincluding a thermoplastic urethane, wherein said second and third layerssandwich the first layer; said membrane being characterized in thatreactive contact in the form of hydrogen bonding occurs along a segmentof the membrane between the first layer and at least one of said secondor third layers.
 14. The barrier membrane according to claim 13, whereinsaid first layer includes up to about 50 wt. % of aliphaticthermoplastic urethane.
 15. The barrier membrane according to claim 14,wherein said first layer includes between about 1 wt. % to about 30 wt.% of aliphatic thermoplastic urethane.
 16. The barrier membraneaccording to claim 15, wherein said first layer includes between about 5wt. % to about 25 wt. % of aliphatic thermoplastic urethane.
 17. Thebarrier membrane according to claim 13, wherein said copolymer ofethylene and vinyl alcohol is selected from the group consisting ofcopolymers including an ethylene content of between about 25 mol. % toabout 48 mol. %.
 18. The barrier membrane according to claim 13, whereinthe aliphatic thermoplastic urethane of said first layer includes atleast one polyester based urethane.
 19. The barrier membrane accordingto claim 13, wherein the thermoplastic urethane of at least one of saidsecond or third layers is selected from the group consisting ofpolyester, polyether, polycaprolactone, polyoxypropylene andpolycarbonate macroglycol based materials and mixtures thereof.
 20. Thebarrier membrane according to claim 13, wherein said first layer has anaverage thickness of between about 0.5 mils to about 10 mils and saidsecond and third layers have an average thickness of between about 5mils to about 100 mils.
 21. The barrier membrane according to claim 13,wherein said second layer also includes an aromatic urethane.
 22. Thebarrier membrane according to claim 13, wherein said first layerincludes: (a) 50 wt. % to about 97 wt. % of at least one ethylene andvinyl alcohol copolymer; (b) 3 wt. % to about 50 wt. % of at least onealiphatic thermoplastic urethane; and (c) up to about 3.0 wt. % of oneor more aromatic urethanes; wherein the total constituency of said firstlayer is equal to 100.0 wt. %.
 23. A method for producing a laminatedbarrier membrane useful for controlling gas permeation therethrough,comprising the steps of: (a) extruding a first layer including a blendof at least one aliphatic thermoplastic urethane and at least onecopolymer of ethylene and vinyl alcohol; and (b) extruding a secondlayer including a thermoplastic urethane such that said first and secondlayers are in physical contact; said barrier membrane beingcharacterized in that reactive contact in the form of hydrogen bondingoccurs along a segment of the membrane between the first and secondlayers.
 24. The method for producing a barrier membrane according toclaim 23, wherein said first layer includes up to about 50 wt. % ofaliphatic thermoplastic urethane.
 25. The method for producing a barriermembrane according to claim 24, wherein said first layer includesbetween about 1 wt. % to about 30 wt. % of aliphatic thermoplasticurethane.
 26. The method for producing a barrier membrane according toclaim 25, wherein said first layer includes between about 5 wt. % toabout 25 wt. % of aliphatic thermoplastic urethane.
 27. The method forproducing a barrier membrane according to claim 23, wherein saidcopolymer of ethylene and vinyl alcohol is selected from the groupconsisting of copolymers including an ethylene content of between about25 mol. % to about 48 mol. %.
 28. The method for producing a barriermembrane according to claim 23, wherein the extrusion of said first andsecond layers is carried out at a temperature of between about 300° F.to about 450° F.
 29. The method of producing a barrier membraneaccording to claim 23, wherein said second layer of thermoplasticurethane is selected from the group consisting of polyester, polyether,polycaprolactone, polyoxypropylene and polycarbonate macroglycol basedmaterials and mixtures thereof.
 30. The method for producing a barriermembrane according to claim 23, wherein said first layer also includesan aromatic thermoplastic urethane.
 31. The barrier membrane accordingto claim 23, wherein said first layer includes: (a) 50 wt. % to about 97wt. % of at least one copolymer of ethylene and vinyl alcohol; (b) 3 wt.% to about 50 wt. % of at least one aliphatic thermoplastic urethane;and (c) up to about 3 wt. % of one or more aromatic thermoplasticurethanes; wherein the total constituency of said first layer is equalto 100 wt. %.
 32. A method for producing a laminated barrier membranehaving improved resistance to gas permeation, comprising the steps of:simultaneously extruding: (1) a first layer including at least onealiphatic thermoplastic urethane and at least one copolymer of anethylene and vinyl alcohol; and (2) a second layer including athermoplastic urethane together such that said first and second layersare in physical contact; whereby said membrane is characterized in thatreactive contact in the form of hydrogen bonding occurs along a segmentof the membrane between said first and second layers.
 33. The method forproducing a barrier membrane according to claim 32, wherein said firstlayer includes up to about 50 wt. % of aliphatic thermoplastic urethane.34. The method for producing a barrier membrane according to claim 33,wherein said first layer includes between about 1 wt. % to about 30 wt.% of aliphatic thermoplastic urethane.
 35. The method for producing abarrier membrane according to claim 34, wherein said first layerincludes between about 5 wt. % to about 25 wt. % of aliphaticthermoplastic urethane.
 36. The method for producing a barrier membraneaccording to claim 32, wherein said copolymer of ethylene and vinylalcohol is selected from the group consisting of copolymers including anethylene content of between about 25 mol. % to about 48 mol. %.
 37. Themethod for producing a barrier membrane according to claim 32, whereinthe extrusion of said first and second layers is carried out at atemperature of between about 300° F. to about 450° F.
 38. The method ofproducing a barrier membrane according to claim 32, wherein said secondlayer of thermoplastic urethane is selected from the group consisting ofpolyester, polyether, polycaprolactone, polyoxypropylene andpolycarbonate macroglycol based materials and mixtures thereof.
 39. Themethod of producing a barrier membrane according to claim 32, whereinsaid first layer has an average thickness of between about 0.5 mils toabout 10 mils and said second layer has an average thickness of betweenabout 5 mils to about 100 mils.
 40. The method for producing a barriermembrane according to claim
 32. wherein said first layer also includesan aromatic thermoplastic urethane.
 41. The barrier membrane accordingto claim 32, wherein said first layer includes: (a) 50 wt. % to about 97wt. % of at least one copolymer of ethylene and vinyl alcohol; (b) 3 wt.% to about 50 wt. % of at least one aliphatic thermoplastic urethane;and (c) up to about 3 wt. % of one or more aromatic thermoplasticurethanes; wherein the total constituency of said first layer is equalto 100 wt. %.
 42. The method for producing a laminated barrier membraneaccording to claim 32, further comprising the step of simultaneouslyextruding a third layer including at least one thermoplastic urethane,whereby said second and third layers sandwich at least a portion of saidfirst layer therebetween.
 43. The method for producing a laminatedbarrier membrane according to claim 42, wherein said first layer has anaverage thickness of between about 0.5 mils to about 10 mils and saidsecond and third layers have an average thickness of between about 5mils to about 100 mils.
 44. An gas-filled cushioning device, comprising:a multi-layer film which is formed into an gas-filled membrane having aninterior compartment capable of receiving at least one capture gasconstituent, said multi-layer film including an outer layer comprised ofa first flexible resilient elastomeric thermoplastic material and abarrier layer comprised of a combination of at least one aliphaticthermoplastic and at least one copolymer of ethylene and vinyl alcohol,said multi-layer film being capable of selectively resisting an outwarddiffusion of said capture gas constituent and permitting an inwarddiffusion pumping of at least one mobile gas constituent.
 45. Thegas-filled cushioning device according to claim 44, wherein said capturegas is nitrogen.
 46. The gas-filled cushioning device according to claim44, wherein said first layer includes up to about 50 wt. % of aliphaticthermoplastic urethane.
 47. The gas-filled cushioning device accordingto claim 46, wherein said first layer includes between about 1 wt. % toabout 30 wt. % of aliphatic thermoplastic urethane.
 48. The gas-filledcushioning device according to claim 47, wherein said first layerincludes between about 5 wt. % to about 25 wt. % of aliphaticthermoplastic urethane.
 49. The gas-filled cushioning device accordingto claim 44, wherein said copolymer of ethylene and vinyl alcohol isselected from the group consisting of copolymers including an ethylenecontent of between about 25 mol. % to about 48 mol. %.
 50. Thegas-filled cushioning device according to claim 44, wherein said secondlayer of thermoplastic urethane is selected from the group consisting ofpolyester, polyether, polycaprolactone, polyoxypropylene andpolycarbonate macroglycol based materials and mixtures thereof.
 51. Thegas-filled cushioning device according to claim 44, wherein said firstlayer also includes an aromatic thermoplastic urethane.
 52. Thegas-filled cushioning device according to claim 44, wherein said firstlayer includes: (a) 50 wt. % to about 97 wt. % of at least one copolymerof ethylene and vinyl alcohol; (b) 3 wt. % to about 50 wt. % of at leastone aliphatic thermoplastic urethane; and (c) up to about 3 wt. % of oneor more aromatic thermoplastic urethanes; wherein the total constituencyof said first layer is equal to 100 wt. %.
 53. The gas-filled cushioningdevice according to claim 44, wherein said first layer including acombination of at least one aliphatic thermoplastic urethane and atleast one copolymer of ethylene and vinyl alcohol has an averagethickness of between about 0.5 mils to about 10 mils and said secondlayer of thermoplastic urethane has an average thickness of betweenabout 5 mils to about 100 mils.
 54. The gas-filled cushioning deviceaccording to claim 44, further comprising a third layer including athermoplastic urethane selected from the group consisting of polyester,polyether, polycaprolactone, polyoxypropylene and polycarbonatemacroglycol based materials and mixtures thereof, said third layer andsaid second layer being disposed so as to sandwich the first layer. 55.In a shoe having an upper and a sole structure, a gas-filled cushioningdevice forming part of said sole structure, comprising: a multi-layerfilm which is formed into a gas-filled membrane having an interiorcompartment capable of receiving at least one capture gas constituent,said multi-layer film including an outer layer comprised of an outerlayer of flexible resilient elastomeric thermoplastic material, an innerlayer comprised of a second flexible resilient elastomeric thermoplasticmaterial, and a barrier layer comprised of a combination of at least onealiphatic thermoplastic urethane and at least one copolymer of ethyleneand vinyl alcohol, said multi-layer film being capable of selectivelyresisting an outward diffusion of said capture gas constituent andpermitting an inward diffusion pumping of at least one mobile gasconstituent, said barrier layer being interposed between and in directcontiguous contact with at least a segment of said outer and innerlayers.
 56. The gas-filled cushioning device according to claim 55,wherein said barrier layer includes up to about 50 wt. % of aliphaticthermoplastic urethane.
 57. The gas-filled cushioning device accordingto claim 56, wherein said barrier layer includes between about 1 wt. %to about 30 wt. % of aliphatic thermoplastic urethane.
 58. Thegas-filled cushioning device according to claim 57, wherein said barrierlayer includes between about 5 wt. % to about 25 wt. % of aliphaticthermoplastic urethane.
 59. The gas-filled cushioning device accordingto claim 55, wherein said copolymer of ethylene and vinyl alcohol isselected from the group consisting of copolymers including an ethylenecontent of between about 25 mol. % to about 48 mol. %.
 60. Thegas-filled cushioning device according to claim 55, wherein at least oneof said inner and outer layers of thermoplastic urethane is selectedfrom the group consisting of polyester, polyether, polycaprolactone,polyoxypropylene and polycarbonate macroglycol based materials andmixtures thereof.
 61. The gas-filled cushioning device according toclaim 55, wherein said barrier layer also includes an aromaticthermoplastic urethane.
 62. The gas-filled cushioning device accordingto claim 55, wherein said barrier layer includes: (a) 50 wt. % to about97 wt. % of at least one copolymer of ethylene and vinyl alcohol; (b) 3wt. % to about 50 wt. % of at least one aliphatic thermoplasticurethane; and (c) up to about 3 wt. % one or more aromatic thermoplasticurethanes; wherein the total constituency of said first layer is equalto 100 wt. %.
 63. The gas-filled cushioning device according to claim55, wherein said barrier layer including a combination of at least onealiphatic thermoplastic urethane and at least one copolymer of ethyleneand vinyl alcohol has an average thickness of between about 0.5 mils toabout 10 mils and said inner and outer layers of thermoplastic urethanehave an average thickness of between about 5 mils to about 100 mils. 64.A barrier membrane having improved resistance to undesired gasgeneration comprising: one layer including a thermoplastic urethane; andanother layer including a blended combination of at least one aliphaticthermoplastic urethane and a polar and partially crystalline material;wherein said membrane is characterized in that reactive contact in theform of hydrogen bonding occurs between the layer including a blendedcombination and the layer including thermoplastic urethane.
 65. Abarrier membrane having improved resistance to undesired gas permeationcomprising: a barrier layer including a combination of at least onealiphatic thermoplastic urethane and at least one copolymer ethylene andvinyl alcohol.
 66. A barrier membrane having improved resistance toundesired gas permeation comprising: a barrier layer including a blendedcombination of at least one aliphatic thermoplastic urethane and a polarand partially crystalline material having gas diffusion properties.